The starting point of this thesis is a neural definition of consciousness, independent of attention or other cognitive functions
that are required for a behavioral report. It is defined as recurrent processing (RP) - which is needed for integration of
information - as opposed to unconscious feedforward processing. As RP is mediated by NMDA receptors, it is hypothesized that
consciousness (according to the neural definition) plays a role in learning. Using EEG, I showed that stimuli that evoked
RP yet were unattended (and therefore unreportable) are learned at the perceptual level, whereas attended yet masked stimuli
(for which RP was blocked) do not show any learning effects. Interestingly, the behavioral learning effect only became apparent
when performance feedback was given. This suggests that the memory trace formed during inattention was latent until reactivated
by behavioral feedback. A follow-up fMRI experiment revealed that performance feedback boosts neural learning effects as well.
In addition, when NMDA receptors are manipulated with ketamine (thereby reducing RP), visual feature integration is diminished
and perceptual learning precluded. Together, these results provide a first step in understanding the benefit of defining the
distinction between unconscious and conscious processing as the divide between feedforward and recurrent processing respectively.
It allows us to understand consciousness on a more fundamental level, by understanding its function: consciousness is needed
for learning. It would be interesting to investigate how far the current findings extend beyond the perceptual learning domain,
and to further elucidate the role of feedback in reconsolidating latent memory traces.

Disclaimer/Complaints regulations

If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let
the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible
and/or remove it from the website. Please Ask the Library, or send a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands.
You will be contacted as soon as possible.